Screenshot applet doesn't work after I use CAS SSO

I add CAS SSO of my company and JIRA SSO works right,but the Screenshot applet doesn't work seems the redirect is not right.

JARS:
cas-client-core-3.3.0.jar
cas-client-integration-atlassian-3.3.0.jar

AND web.xml ，seraph-config.xml is right

Java Plug-in 1.6.0_18
JRE VERSION 1.6.0_18-b07 Java HotSpot(TM) Client VM
用户主目录 = C:\Users\890150
----------------------------------------------------
c: 清除控制台窗口
f: 终结在结束队列上的对象
g: 垃圾收集
h: 显示此帮助消息
l: 转储类载入程序列表
m: 打印内存使用
o: 触发日志记录
q: 隐藏控制台
r: 重新载入策略配置
s: 转储系统和部署属性
t: 转储线程列表
v: 转储线程堆栈
x: 清除类载入程序高速缓存
0-5: 设置跟踪级别为<n>
----------------------------------------------------
载入：找不到类 com.atlassian.jira.screenshot.applet.ScreenshotApplet.class。
java.lang.ClassNotFoundException: com.atlassian.jira.screenshot.applet.ScreenshotApplet.class
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
异常：java.lang.ClassNotFoundException: com.atlassian.jira.screenshot.applet.ScreenshotApplet.class